1. Field of the Invention
The present invention relates to a circuit device, and particularly to a circuit device in which a hybrid integrated circuit formed on an upper surface of a circuit board is sealed with a case member.
2. Description of the Related Art
The configuration of a hybrid integrated circuit device 150 employing a case member 111 is described with reference to FIG. 7. The hybrid integrated circuit device 150 includes: a substrate 101 made of a metal, such as aluminum; an insulating layer 102 formed so as to cover the upper surface of the substrate 101; a conductive pattern 103 formed on the upper surface of the insulating layer 102; and a circuit element 110 such as a transistor electrically connected to the conductive pattern 103. The circuit element 110 is sealed with the case member 111 and a sealing resin 108.
Specifically, the case member 111 has an approximately frame-like shape and is in contact with the side surface of the substrate 101. In addition, in order to secure a sealing space over the upper surface of the substrate 101, the upper end part of the case member 111 is positioned above the upper surface of the substrate 101. Then, the sealing resin 108 is filled in the space surrounded by the case member 111 above the substrate 101 so as to cover the circuit element 110 such as a semiconductor element. With this configuration, the circuit element mounted on the upper surface of the substrate 101 can be sealed with a sealing resin 108 for filling in the space surrounded by the case member 111 or the like, even if the substrate 101 is relatively large.
This technology is described for instance in Japanese Patent Application Publication No. 2007-036014.
In the hybrid integrated circuit device 150 described above, a power transistor, such as an insulated gate bipolar transistor (IGBT), and a driver IC for driving this power transistor are mounted on the upper surface of the substrate 101. In addition, a controlling element, such as a microcomputer for controlling this driver IC, is mounted on the mounting substrate side on which the hybrid integrated circuit device 150 is mounted. Because of this configuration, the area required to mount a circuit which controls for driving a load, such as a motor, has to be large on the mounting substrate side.
In order to solve the above-described problem, provided is a method in which the microcomputer is fixed, for example, to the upper surface of the substrate 101 together with the above-described power transistor or driver IC. This configuration allows the power transistor and the microcomputer to be incorporated into one hybrid integrated circuit device, thereby requires smaller area for mounting the control circuit. However, if the power transistor and the microcomputer are fixed to the upper surface of the same substrate 101, a heat generated in the power transistor is conducted to the microcomputer via the substrate 101 made of a metal such as aluminum. In addition, the heat generated in the power transistor is conducted to the microcomputer via the sealing resin 108 for sealing the entire device. As a result, the microcomputer heated by the power transistor might cause a misoperation.